Bristles of an applicator produced in a laser milled mold

ABSTRACT

A method for injection molding a plastic applicator with a ball of bristles produced integrally with a support handle. The mold consists of two opposing parts. The mold is machined by means of a laser. The mold is laser drilled with gradually decreasing depths of bores from the midpoint of the mold parts outwardly.

[0001] This application is a continuation-in-part of patent applicationSer. No. 09/395,959, filed Sep. 14, 1999.

FIELD OF THE INVENTION

[0002] The invention relates to molding or replication tooling. Inparticular, the invention relates to laser machined mold or replicationtooling useful for the ultimate production of structured articles, suchas bristles of a liquid applicator.

BACKGROUND OF THE INVENTION

[0003] Molding or replicating tooling has been produced by severaldifferent techniques. These techniques include, for instance, machiningand chemical processing. Machining is accomplished by cutting with astylus or microfilming into a substance, such as a mold surface.

[0004] Devices which accomplish such machining are either manually,mechanically or electronically controlled. These devices are capable ofproducing surfaces with optical grade precision, depending upon theirquality. U.S. Pat. No. 4,938,563 to Nelson et al discloses the use of adiamond stylus for cutting into a flat metal surface of a master tool ormold. U.S. Pat. No. 4,959,265 to Wood et al. discloses the use of amicrodrill to form the mold for a pressure-sensitive adhesive tapefastener backing. U.S. Pat. No. 5,077,870 to Melby et al relates to theuse of a microdrill to form a metal mold used to produce mushroom-typehook strips for a mechanical fastener. These methods are considered slowfor all but the simplest replications. In addition, replacement of thestylus and drill bits is expensive and adds to the cost of themachining. Another method for the production of microstructured toolingrelates to the use of sharpened or shaped structures, such as pins orrods, being forced into a relatively soft medium, such as described inU.S. Pat. No. 3,235,438 to Wisotzky. This patent also illustrates thetraditional, multi-step approach to the production of a microreplicationmolding or tooling. A primary negative mold is prepared by forcing thestructures into the relatively soft medium. Intermediate positive mastermolds are made from the negative primary mold and are then joinedtogether to form a large positive mold. A large negative mold is thenproduced from the large positive mold, which is then used to producereplicated articles. Preparation of the final negative mold requiressignificant time and cost.

[0005] Lasers have been used to machine some finished articles, such asfilters, award plaques, rubber stamps, and stencils, but lasers have notbeen used to make molds or replication toolings. U.S. Pat. No. 5,792,411to Morris et al calls for laser use to cut cavities is a substrate forproducing tooling which can be used for microreplication purpose.

[0006] Such toolings has not been shown to be used to produce a truemold into which a thermoplastic resin is injected in order to produce anelongated handle having a bristle portion, the latter acts as a liquidcarrier.

SUMMARY OF THE INVENTION

[0007] This invention relates to a method of manufacturing amicroreplication master tooling suitable for manufacturing replicatedarticles by machining a substrate surface with a laser light source toproduce a plurality of laser drilled indentations on surface extendingfrom the substrate surface into the substrate itself.

[0008] The invention also relates to a method of manufacturing amicroreplication master tooling suitable for manufacturing replicatedarticles by machining a unitary substrate surface to produce at leastone geometric structure having side surfaces extending into thesubstrate, such that the substrate provides structural means forproducing articles replicated from the master tooling. The substrate maycomprise two mating surfaces forming a mold into which an injectablethermoplastic material may be charged.

[0009] The invention also relates to a method of manufacturing anarticle such as a bristle containing member from a microreplicationmaster tooling by machining tooling mold surfaces with a laser lightsource to produce a geometric structure in the mold surfaces. The moldis closed and a heated thermoplastic material is then applied into themold through an entrance orifice. The thermoplastic is permitted tosolidify to produce a replicated article of the tooling which may be atiny bristled liquid applicator, and the thereby produced applicator isremoved from the tooling or mold.

[0010] The invention further relates to an article, which is a bristlesapplicator that is manufactured by the method.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is a perspective view of the open mold with a plurality ofindentations.

[0012]FIG. 2 is a schematic cross-section of the mold being machined bya laser beam.

[0013]FIG. 3 is the same cross-sectional view as FIG. 2 wherein the saidmold is further along in being machined.

[0014]FIG. 4 is another embodiment showing laser machining of geometriesof the same depth.

[0015]FIG. 5 is another embodiment of FIG. 4 showing machining with alaser of less shallow geometric shapes.

[0016]FIG. 6 depicts a cross-section of the mold laser machined withvarying depths.

[0017]FIG. 7 is the same cross-sectional view of FIG. 6 loaded with athermoplastic material.

[0018]FIG. 8 depicts the solidified thermoplastic material removed fromthe mold.

[0019]FIG. 9 depicts the mold of the present invention as it appearsprior to closing.

DETAILED DESCRIPTION OF THE INVENTION

[0020] Attention is directed to FIG. 1 which shows, generally, one partof a mold 11. The mold is shown as a single producing item but inpractice is part of a large array whereby a plurality of applicators maybe molded at essentially the same time.

[0021] The mold has a proximal end portion 14 and a distal end portion15. The proximal end portion 14 has a linear elongated groove 16. Thegroove 16 extends to the distal end portion 15.

[0022] The distal end portion 15 has a plurality of cylindricaldepressions 17 of varying, preselected depths which have been cutthereinto by a laser light in mold depression 12 as explained more fullyin FIGS. 2, 3, 4 and 5. The groove 16 proximal end portion terminates inan entrance conduit 18 through which moldable material is injected whenthe mold is closed.

[0023] The mold 11 has a confronting part, not shown by FIG. 1 which isa mirror image of mold 11 and overlies it to complete the mold intowhich moldable material is injected which is a thermoplastic resinousmaterial such as nylon, propylene or polyethylene.

[0024] FIGS. 2-5, depict the fabrication of the mold by laser lighttechnology.

[0025] The Figures depict a cross-sectional view of distal end portion15 of the mold.

[0026] A laser light source 20 is shown as the machining tool, i.e., thedrill means for drilling cylindrical depressions 17 to variouspredetermined depths. In FIG. 2 one can see that the depressions 17 areof less depth towards one side then progress to a lesser depth as thedepressions on the opposite side.

[0027] In FIG. 5 the depressions 17 may be of a maximum depth at oneside and then be of a lesser depth on the other side.

[0028] The drilling, by the laser may be step-wise progressive or, it iscontemplated that an array of laser light sources can be used to drill agreat number of bores or depressions at one time.

[0029] The depressions depict a disc-like concavity. The drilled boresvary in depth progressively in a gradual decreasing progression from themidpoint of the disc concavity outwardly.

[0030] Furthermore, a great number of the molds can be produced at thesame time or progressively so that a plurality of applicators may beproduced simultaneously to thereby increase efficiency of operation.

[0031] While it is contemplated that the mold would be fabricated of ametal, various thermosetting plastic materials can be used as they lendthemselves to relatively easy laser drilling.

[0032]FIGS. 6 and 7 depict a cross-sectional view of mold 11 which isdepicted as overlain with a minor image mold portion 11A to complete themold prior to injection with the thermoplastic material. Thecross-sectional parts shown by FIGS. 6 and 7 is through distal endportion 15. As stated, FIG. 6 shows the mold in an empty condition,while FIG. 7 shows the mold loaded with a thermoplastic material.

[0033] After injection the thermoplastic material is permitted to coolin order to solidify the material. Then in from FIG. 8 one can see themolded material as it looks upon its removal from the mold, i.e., havinga plurality of bristles 19 on an elongated linear handle.

[0034]FIG. 9 depicts the mold 11 with an upper mirror image 11Athereabove. The two parts of the mold may be hinged together or may becompletely separable.

[0035] The applicators resulting from the present method are generally,tiny, having, a thin handle of three to 6 inches and a bristle portiondescribing a ball or cylindrical configuration. Prior art applicators ofthis type are constructed by applying bristles to an end of a plasticstick employing various adhesives or heating the ends of the stitches toa semi-fluid condition upon which the bristles are deposited and adheredunder the aegis of electrostatic attraction.

[0036] The present method accomplishes the production of an entirelyintegral unit of similar material both for the stick or handle and thebristles.

[0037] Laser machining of microreplication tooling is advantageous inthat the molds may be produced at a high speed at a significantlyreduced cost. In addition, pattern flexibility is achieved since a widevariety of geometric structures may be machined into themicroreplication tooling or mold. By using a laser to machine a mold ofthermosetting material, for instance, provides profile flexibility inthe geometric structures. Vaporization of the resin by laser lightremoves the material from the machined cavity producing a minimum flashresidue, which is easily cleaned and removed.

What is claimed is:
 1. A method for producing a thermoplastic applicatorhaving a plurality of integral bristles on an elongated membercomprising: providing a mold consisting of two elongated parts, each ofsaid mold parts having a proximate end portion and a distal end portion,milling an elongated groove from said proximate end portion of each partand terminating at substantially said distal portion of each of saidmold parts, milling a disc concavity in said distal portion of each ofsaid mold parts, drilling a plurality of spaced bores with coherentlight into each of said disc concavities of each mold part, said boresbeing of gradually decreasing depth from a midpoint of each discconcavity outwardly, closing said mold parts whereby the discconcavities of the distal portions containing said bores are inconfronting relationship with one another, providing an entrance intosaid closed mold in said proximate end portion of a mold part, injectinga moldable material into said entrance of said closed mold to fill saidmold and said bores, permitting said moldable material to solidify,opening said mold, thereafter, freeing said solidified material fromsaid mold parts.